576 



CEPHALOPODA. 



(1541.) The alimentary canal presents the same general structure in 

 all the Cephalopod families. The oesophagus (fig. 287, A, d ; fig. 289, s), 

 derived from the posterior part of the fleshy mass of the mouth, passes 

 through a ring formed in the cranial cartilage ; or else, as in Nautilus, 

 is partially embraced by processes derived therefrom. It soon dilates 

 into a capacious crop (fig. 289, t), the walls of which are glandular ; and 



Fig. 289. 



Anatomy of Nautilus Pompilius (after Owen) : a, b, c, d, f, section of the mantle ; 

 g, large circular flap surrounding the mouth, supporting h, a series of retractile tentacula; 

 t, smaller lobes, also provided with retractile tentacula; kk,l, presumed olfactory apparatus; 

 ?n, circular lip ; M, o, horny mandibles ; p, q, r, muscular apparatus of the mouth ; , oasophagus ; 

 /, crop; r, gizzard; w w, intestine; x, anus; y, pancreatic organ; z z, lobes of the liver. 



being lined with a mucous membrane that is gathered into longitudinal 

 plicae, this organ readily admits of considerable dilatation. 



